Crows are scary smart. My dad had a infestation of a flock of crows in his backyard. Like Hitchcock's, The Birds, hundreds would use his fountain as a toilet and generally make a mess. He finally killed one and left it in his yard. And the damndest thing, was they left. They stayed just at the edge of his property and stared. For about two weeks. You would walk outside and it was just like the movie. All you could hear was the silent ruffling of feathers. Scared the feces out of me. Very creepy.